Crystal microstructure, infrared absorption, and microwave electromagnetic properties of (La_(1-x)Dy_x)_(2/3)Sr_(1/3)MnO_3

The manganite perovskite polycrystal samples of （La1-xDyx）2/3Sr1/3MnO3 （x = 0, 0.1, 0.2, 0.35, and 0.5） doped with Dy were prepared by solid state reaction in atmosphere to measure their X-ray diffraction （XRD） patterns, scanning electric microscope （SEM） images, infrared absorption spectra, and microwave electromagnetic properties. The displacement of the XRD peaks of the samples was found, and the 2θ increases from 0.05o to 0.5o. The grains of undoped La2/3Sr1/3MnO3 not only have the greatest size, but also the most regular shape. The size of the grains decreases as the Dy doping content increases from 0 to 0.5. The infrared absorption spectra of all samples were measured at room temperature. An absorption peak corresponding to the stretching vibration mode of Mn-O bonds appears within the range of 591-629 cm-1. The absorption peak shifts from a higher frequency to a lower one with the decrease of the average ionic radius of A-site. The frequency de- pendence of microwave-absorbing properties, imaginary components of the complex magnetic permeability μ＂ and dielectric permeability ε＂ for all samples was measured at room temperature from 8 to 13 GHz. The results show that the loss of microwave absorption can be attrib- uted to both the magnetic and electric losses. The increase of Dy content not only enhances the microwave absorption but also causes the displacement of the absorption peaks.

Deposition of hexagonal boron nitride thin films on silver nanoparticle substrates and surface enhanced infrared absorption

Silver nanoparticle thin films with different average particle diameters are grown on silicon substrates. Boron nitride thin films are then deposited on the silver nanoparticle interlayers by radio frequency （RF） magnetron sputtering. The boron nitride thin films are characterized by Fourier transform infrared spectra. The average particle diameters of silver nanoparticle thin films are 126.6, 78.4, and 178.8 nm. The results show that the sizes of the silver nanoparticles have effects on the intensities of infrared spectra of boron nitride thin films. An enhanced infrared absorption is detected for boron nitride thin film grown on silver nanoparticle thin film. This result is helpful to study the growth mechanism of boron nitride thin film.

Magnetism, Electronic Transport and Infrared Absorption Spectra in Perovskite Manganite La_(0.67-x)Dy_xCa_(0.33)MnO_3 (x=0～0.6)

Polycrystalline samples La0.67-xDyxCa0.3MnO3 (x=0～0.6) were prepared by traditional solid-state reaction method. The magnetization and resistivity of the samples were measured by PPMS (Quantum Design). The infrared absorption spectra (temperature scope: 20～300 K, frequency: 400～4400 cm-1) were collected by WQF-410 Fourier Transform Spectrophotometer. The substitution of Dy on La sites results in a decrease of the Curie temperature Tc and the magnetization, and also induces cluster-glass behaviors. The resistivity of the compounds is enhanced by Dy doped. Infrared absorption spectra provide the evidence of the variety of Mn-O-Mn bond length due to the Dy substitution and temperature changing. These results suggest that all of the magnetic coupling between Dy and Mn sublattice and La-Dy average ionic radius contribute to the magnetic and electronic character.

Residual compressive stress and intensity of infrared absorption of cubic BN films prepared by plasma enhanced chemical vapor deposition

Theoretical and experimental investigations on the dependence of the intensity of infrared （IR） absorption of poly- crystalline cubic boron nitride thin films under the residual compressive stress conditions have been performed. Our results indicate that the intensity of the IR absorption is proportional to the total degree of freedom of all the ions in the ordered regions. The reduction of interstitial Ar atom concentration, which causes the increase in the ordered regions of cubic boron nitride （cBN） crystallites, could be one cause for the increase in the intensity of IR absorption after residual compressive stress relaxation. Theoretical derivation is in good agreement with the experimental results concerning the IR absorption intensity and the Ar interstitial atom concentration in cubic boron nitride films measured by energy dispersion X-ray spec- troscopy. Our results also suggest that the interstitial Ar is the origin of residual compressive stress accumulation in plasma enhanced cBN film deposition.

Tuning infrared absorption in hyperbolic polaritons coated silk fibril composite

Advanced textiles for thermal management give rise to many functional applications and unveil a new frontier for the study of human thermal comfort.Manipulating the coated quasi-particles between the composite components offers a platform to study the advanced thermoregulatory textiles.Here,we propose that coating the hyperbolic polariton can be an effective tool to tune infrared absorption in hexagonal boron nitride-coated silk composite.Remarkably,we achieve significant tuning of the infrared absorption efficiency of silk fibrils through the designed hexagonal boron nitride film.The underlying mechanism is related to resonance coupling between hyperbolic phonon polaritons.We find a notably high infrared absorption efficiency,nearly 3 orders larger than that without hBN coating,which can be achieved in our composite system.Our results indicate the promising future of advanced polariton-coated textiles and open a pathway to guide the artificial-intelligence design of advanced functional textiles.

First-principles Study on Infrared Absorptions of Transition Metal-doped ZnO with Oxygen Vacancy

Using first-principle theory, the infrared absorptions of transition metal （Mn, Fe, Co, Ni）-doped ZnO were investigated. The results indicate that the absorptions of Mn- and Co-incorporated ZnO without oxygen vacancy are reduced, while those of Fe- and Ni-doped ZnO are raised. This is consistent with the previous experimental results. The effects of oxygen vacancy on the absorptions of the doped systems were predicted. When a neutral oxygen vacancy is introduced, all doping elements decrease the absorptions. On the contrary, the absorptions of the doped systems are enhanced if the vacancies are charged. Degraded absorptions can be obtained by increasing the permeability. However, the appearance of anti-bonding states may cause enhanced absorptions. In the current study, Mn-doped ZnO is the most suitable for use as low infrared absorption materials.

Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy: a Powerful Technique for Bioanalysis

Attenuated total reflection surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS)has recently been proven to be a powerful tool for bioanalysis.It enables in situ and in real-time observation of dynamic processes occurring on specific interface,revealing rich structural and functional information of biomolecules at sub monolayer level.The aim of this general review was to give an overview of the cutting edge applications of ATRSEIRAS.We start with description of the basic configuration of the standard ATR-SEIRAS platform.The enhanced mechanisms and methods to fabricate enhanced substrates are then presented.We discuss the recent developments,challenges and applications of ATR-SEIRAS in bioanalysis,mainly focusing on DNA analysis,protein behavior and cell properties.Finally,further development of the ATRSEIRAS technique with enhanced sensitivity,improved time and spatial resolutions will be prospected.

Resonant perfect absorption of molybdenum disulfide beyond the bandgap

Light absorption and radiation are fundamental processes in optical science and engineering.Materials with perfect absorption properties play an important role in numerous optical applications.Following the meteoric rise of MoS_(2)material,global opportunities and challenges coexist due to its extremely weak light-matter interaction capability beyond its energy band.In this work,we designed a kind of sandwich resonance structure and investigated MoS_(2)as a perfect absorber in the infrared spectrum that should be transparent according to the optical band theory.The infrared absorption properties of W or Au/MoS_(2)/Au models at 800 nm-2400 nm were systematic simulated.By optimizing the structural parameters,the resonant wavelength of perfect absorption can be modulated from 830 nm to 1700 nm with angle insensitivity and polar independence.Moreover,we discovered that the bandwidth of absorption exceeding 50%of the W-top model reaches500 nm,while that of the Au-top model is less than 100 nm,indicating that the top metal material has a great influence on the resonance absorption spectrum.Our work provides a practical route for enhancing and manipulating the light-matter interactions of low-dimensional materials beyond their own band gaps,which will be critical in the future design and implementation of optoelectronic devices and systems.

SYNTHESIS AND CHARACTERIZATIONS OF NEAR INFRARED ABSORBING POLYMERS

A series of near infrared (NIR) absorbing dinuclear ruthenium dicarbonylhydrazine complexes (DCH-Ru),[{Ru(bpy)_2)_2μ-DCH]^(n+) (where bpy = 2,2'-bipyridinc and n = 2, 3 or 4), were prepared. The DCH-Ru complexes areelectrochromic in the NIR region with a high absorption coefficient at 1550-1600 nm typically over 10000 M^(-1)cm^(-1). DCH-Ru complex polymers with good NIR electrochromic properties were also obtained and processed to make a device foroptical attenuation at a wavelength of 1550 nm. The potential of these DCH-Ru polymers for use in a variable opticalattenuator has been demonstrated with an attenuating power at the 1550-nm telecommunication wavelength over 7.0 dB permicron of polymer film thickness. Other classes of NIR active materials are the pentacenediquinones and the correspondingpoly(ether pentacenediquinone)s. These polymers can be electrochemically reduced to the corresponding semiquinone(radical anion) having NIR absorption within a telecom window (e. g., 1310 nm).

Determination of spin-orbit splitting Δ_0 of valence band at Γ for gallium phosphide nanoparticles using fluorescence and infrared spectroscopes

The value of spin-orbit splitting Δ 0 of gallium phosphide （GaP） nanoparticles was determined. The information concerning the spin-orbit splitting of the valence band at Γ was acquired using fluorescence and infrared spectroscopes. Detailed investigation on the fluorescence characteristics under ultraviolet photoexcitation reveals that two doublets of emission transitions are related to the spin-orbit splitting of the valence band. The origin of two broad violet emissions, 3.00 and 3.10 eV, can be attributed to the direct transitions near the Γ point of the Brillouin zone between the Γ 1 conduction band and Γ 15 valance band, that is, Γ 6c –Γ 8v and Γ 6c –Γ 7v , respectively. The origin of two blue emissions, 2.74 and 2.64 eV, can be attributed to the indirect transitions between the X 1 conduction band and Γ 15 valance band, that is, Δ 5c –Γ 8v and Δ 5c –Γ 7v , respectively. Based on these transitions, the spin-orbit splitting Δ 0 of the GaP nanoparticles is determined as 0.10 eV. The infrared spectrum of the GaP nanoparticles shows a band at 817 cm -1 which is assigned to the transition between the Γ 7v and Γ 8v valence band maxima. It follows therefore that the spin-orbit splitting Δ 0 is 0.10 eV.

MOCVD Ga_xIn_(1-x)As_(1-y)Sb_y Alloys and the Infrared Detector

Ga_xIn_(1-x)As_(1-y)Sb_y alloys have been grown by atmospheric pressure MOCVD on n-GaSb(Te-doped) substrate.The sohd composition was determined by using electron microprobe.The alloys of GalnAsSb with composition in miscibility gap were successfully grown.The optical properties of Ga_xIn_(1-x)As_(1-y)Sb_y lavers were characterized by the photoluminescence and the infrared absorption.The spectral responses of p^+-GaInAsSb/p-Ga_xIn_(1-x)As_(1-y)Sb_y/n-GaSb detectors showed wavelength cut off at 2.4μm and detectivity- D~*=5×10~8 cmHz^(1/2)/W at room temperature.

Synthesis and Characteristics of Diamond-like Carbon Films Deposited on Quartz Substrate

Diamond-like carbon (DLC) films are deposited on quartz substrate using pure CH4 in the surface wave plasma equipment. A direct current negative bias up to -90 V is applied to the substrate to investigate the bias effect on the film characteristics. Deposited films are characterized by Raman spectroscopy, infrared (IR) and ultraviolet-visible absorption techniques. There are two broad Raman peaks around 1340 cm-1 and 1600 cm-1 and the first one has a greater sp3 component with an increased bias. Infrared spectroscopy has three sp3 C-H modes at 2852 cm-1, 2926 cm-1 and 2962 cm-1, respectively and also shows an intensity increase with the negative bias. Optical band gap is calculated from the ultraviolet-visible absorption spectroscopy and the increased values with negative bias and deposition time are obtained. After a thermal anneal at about 500℃ for an hour to the film deposited under the bias of-90 V, we get an almost unchanged Raman spectrum and a peak intensity-reduced IR signal, which indicates a reduced H-content in the film. Meanwhile the optical band gap changed from 0.85 eV to 1.5 eV.

Computer study of the formation of water-ammonia clusters and their dielectric properties

The absorption of one to six ammonia molecules by the （H2O）50 cluster is studied by the molecular dynamics method under near-atmospheric conditions. The capture of NH 3 molecules by a water cluster produces an increase in the integrated intensity of IR absorbance, substantially decreases emission power in the frequency range of 0≤ω≤3500cm-1,and transforms a continuous reflectance spectrum into a banded one. Adsorption of ammonia molecules by water clusters greatly diminishes the number of electrons that are active with respect to electromagnetic radiation. The present results are also compared with the experimental findings wherever available.

C-H complex defects and their influence in ZnO single crystal

Infrared absorption local vibration mode（LVM） spectroscopy is used to study hydrogen related defects in n-type ZnO single crystal grown by a closed chemical vapor transport（CVT） method under Zn-rich growth conditions, in which carbon is used as a transport agent. Two C-H complex related absorption peaks at 2850 cm-1and 2919 cm-1 are detected in the sample. The formation of the C-H complex implies an effect of carbon donor passivation and formation suppression of H donor in ZnO. The influence of the complex defects on the electrical property of the CVT-ZnO is discussed based on Hall measurement results and residual impurity analysis.

Discontinuous transition between Zundel and Eigen for H5O2^+

The hydrated-proton structure is critical for understanding the proton transport in water.However,whether the hydrated proton adopts Zundel or Eigen structure in solution has been highly debated in the past several decades.Current experimental techniques cannot directly visualize the dynamic structures in situ,while the available theoretical results on the infrared(IR)spectrum derived from current configurational models cannot fully reproduce the experimental results and thus are unable to provide their precise structures.In this work,using H5O2^+ as a model,we performed first-principles calculations to demonstrate that both the structural feature and the IR frequency of proton stretching,characteristics to discern the Zundel or Eigen structures,evolve discontinuously with the change of the O–O distance.A simple formula was introduced to discriminate the Zundel,Zundel-like,and Eigen-like structures.This work arouses new perspectives to understand the proton hydration in water.

Correlation between the Concentrations of Ionized EL2 and Carbon Acceptor in Undoped Semi－insulating LEC GaAs

Undoped semi-insulating (SI) LEC GaAs samples were investigated. The concentrations of ionized EL2and carbon acceptor were measured by multiple wavelength infrared absorption and local vibrational modeinfrared absorption methods. The results indicate that for the same sample the ionized EL2 concentration([EL2￣+]) is higher than the carbon acceptor concentration ([C]). The value of [EL2￣+]-[C] is of the order ofmagnitude of 10￣(15) cm￣(-3), which means that acceptors other than carbon exist with a concentration of10￣(15) cm￣(-3) in the samples. This is in conflict with the conventional 3-level compensation model. The radialdistribution of [EL2￣+] was investigated. The radial distribution of carbon acceptor does not present any regu-larity.

Spectroscopy system based on a single quantum cascade laser for simultaneous detection of CO and CO_2

A quantum cascade laser（QCL） based system for simultaneous detection of CO and CO_2 is developed.The QCL can scan over two neighboring CO（2055.40 cm^（-1）） and CO_2（2055.16 cm^（-1）） lines with a single current scan.The wavelength modulation spectroscopy（ f = 20 k Hz） is utilized to enhance the signal-to-noise ratio.A white cell with an effective optical path length of 74 m is used.The calibration of the sensor is performed and minimum detection limits of 1.3 ppb（1 × 10^（-9））for CO and 0.44 ppm（1 × 10^（-6）） for CO_2 are achieved.

Spatial Distribution of EL2 Defect in Semi-insulating GaAs

It has advantages of accuracy, rapidity and non-destruction that EL2 distribution in semi-insulating LECGaAs crystal has been measured by near infrared absorption method with a high spatial resolution. Now EL2defect existed in all wafer is directly observed by 1 .0972 μm and 2 μm absorption curves obtained from a suc-cessive and automatical horizontal scan across the different bands parallelly ranged with tbe diameter of asemi-insulating GaAs wafer. Not only EL2 distribution across the wafer corresponding with that of dislocationdensities has been indicated but also the fine structure found.

Ultrasonic absorption with infrared divergence in cluster spin glass

The infrared divergence response theory is applied to reorientational relaxation process of magnetic clusters in cluster spin glass(CoF2)0.5 (BaF2)0.2 (NaPO3)0.3 to study the behaviour of low temperature ultrasonic absorption in this system . Our calculation results showed that the reorientational relaxation process makes the main contributions to the magnetic part of the ultrasonic absorption for T < 4.0 K ; as for T > 4.0 K , the contributions of the internal process inside the clusters must be considered.

Cu/Mo2C synthesized through Anderson-type polyoxometalates modulate interfacial water structure to achieve hydrogen evolution at high current density

The development of efficient non-precious metal catalysts is important for the large-scale application of alkaline hydrogen evolution reaction(HER).Here,we synthesized a composite catalyst of Cu and Mo_(2)C(Cu/Mo_(2)C)using Anderson-type polyoxometalates(POMs)synthesized by the facile soaking method as precursors.The electronic interaction between Cu and Mo_(2)C drives the positive charge of Cu,alleviating the strong adsorption of hydrogen at the Mo site by modulating the d-band center of Mo_(2)C.By studying the interfacial water structure using in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS),we determined that the positively charged Cu crystals have the function of activating water molecules and optimizing the interfacial water structure.The interfacial water of Cu/Mo_(2)C contains a large amount of free water,which could facilitate the transport of reaction intermediates.Due to activated water molecules and optimized interfacial water structure and hydrogen adsorption energy,the overpotential of Cu/Mo_(2)C is 24 mV at a current density of 10 mA·cm^(-2) and 178 mV at a current density of 1000 mA·cm^(-2).This work improves catalyst performance in terms of interfacial water structure optimization and deepens the understanding of water-mediated catalysis.